Surfactants are widely used in aqueous based personal care, household, and industrial products. They are typically used as wetting agents, detergents, and emulsifiers. In personal care cleansing products (e.g., shampoos, body washes, facial cleansers, liquid hand soaps, etc.) the surfactant is often the most important component because it provides many of the cleansing attributes of the composition.
Although in principle any surfactant class (e.g., cationic, anionic, nonionic, amphoteric) is suitable in cleansing or cleaning applications, in practice most personal care cleansers and household cleaning products are formulated with anionic surfactants or with a combination of an anionic surfactant as the primary detersive agent with one or more secondary surfactants selected from the other surfactant classes. Anionic surfactants are often used as detersive agents in cleansers and cleaning products because of their excellent cleaning and foaming properties. From the consumer's perspective, the amount and stability of the foam directly relates to the perceived cleaning efficiency of the composition. Generally speaking, the larger the volume of foam produced and the more stable the foam, the more efficient is the perceived cleaning action of the composition. This presents a potential problem in low-surfactant formulations, as foam volume tends to decrease with decreasing surfactant concentration.
Sulfate-based surfactants (such as, for example, sodium lauryl sulfate and sodium lauryl ether sulfate) are particularly popular because of their effectiveness in cleansing, foam production, and stability. Personal care cleansers containing sulfate-based surfactants are also generally easy to thicken with typical thickeners, such as salt and cellulose-based materials. Nonetheless, these particular surfactants can be harsh and irritating to skin. For instance, over-use of sulfate-based surfactants can cause needless drying to the face and scalp, and contribute to color fading and drying of hair. Eliminating sulfate surfactants from cleansing compositions has been challenging because sulfate-free compositions typically have poor foaming properties, are difficult to thicken, and may not provide the desired degree of clarity or transparency. Also, the cleansing ability of sulfate-free composition are often sub-optimal.